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  • Title: The formation of enzyme-bound and medium pyrophosphate and the molecular basis of the oxygen exchange reaction of yeast inorganic pyrophosphatase.
    Author: Janson CA, Degani C, Boyer PD.
    Journal: J Biol Chem; 1979 May 25; 254(10):3743-9. PubMed ID: 220217.
    Abstract:
    Yeast inorganic pyrophosphatase, with 10 mM 32Pi and 10 mM Mg2+ present at pH 7.3 TO 7.6, rapidly forms enzyme-bound pyrophosphate equivalent to about 5% of the total catalytic sties on the two enzyme subunits. The enzyme thus appears to bind PPi so as to favor thermodynamically its formation from Pi. The enzyme catalyzes a measurable equilibrium formation of free PPi at a much slower rate. Under similar conditions, the enzyme catalyzes a rapid exchange of oxygen atoms between Pi and water with the relative activation by metals being Mg2+ greater than Zn2+ greater than Co2+ greater than Mn2+. Millisecond mixing and quenching experiments demonstrate that the rate of formation and cleavage of the enzyme-bound PPi is rapid enough to explain most or all of the oxygen exchange reaction.
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